The perinatal period is a time of rapid development and reorganization of the nervous system under the influence of genetic, neural, hormonal and environmental factors. Because of the plastic nature of the nervous system at this time, it is likely to be more vulnerable to environmental influences such as stress which evoke a coordinated response of the nervous and the endocrine systems. The proposed research will first describe the normal development of the sympatho-adrenomedullary system and some of the influences which regulate its development. The study will then test the hypothesis that an environmental factor in the form of a stressful experience during a period of vulnerability can permanently alter this system. Stress in the form of immobilization will be administered to neonatal rats during the first three weeks of age. After periods of time ranging up to 30 days following the stressful event the preganglionic systems of the spinal cord will be analyzed for organization and patterns of synaptic contact. In addition, the peripheral target of the spinal autonomic nervous system, the adrenal gland will also be examined. The analysis will include both neurochemical methods and morphological methods at the light and electron microscopic levels. The profile of organization as well as the pattern of development of the spinal cord and aminergic system of the stressed animal will be compared with that of unstressed animals. Since there are preliminary data indicating that perinatal stress can permanently alter some aminergic system components as well as behavior, it is expected that the proposed research will describe more thoroughly the nature of the nervous system changes as well as correlative adrenal medullary events. This greater understanding of the effects of stress offers the hope of establishing the links between being exposed to a stressful event and developing a mental or cardiovascular disease consequence. This knowledge is directly relevant to devising strategies to treat or to prevent damaging stress responses and their sequelae.